Motor vehicles – Steering by driving – Auxiliary steering motor
Reexamination Certificate
2002-05-17
2004-12-14
Morris, Lesley D. (Department: 3611)
Motor vehicles
Steering by driving
Auxiliary steering motor
C180S006200, C180S006260, C056S010800
Reexamination Certificate
active
06830115
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an axle driving apparatus comprising a pair of axles differentially connected to each other, a propelling transmission mechanism for rotating both the axles together at various speeds in the same direction alternatively selected from two opposite directions for forward and backward traveling of the vehicle, and a steering transmission mechanism for transmitting oppositely directive forces to the respective axles so as to generate a difference of rotational speed between the axles, and wherein the axle driving apparatus is provided for a vehicle (e.g., a mower tractor, installed with a belt type stepless transmission).
Also, the present invention relates to a steering mechanism of a caster which is available for a working vehicle such as a mower tractor requiring a small turn radius, wherein the working vehicle is provided with an axle driving apparatus comprising a propelling transmission mechanism that transmits propelling force to both mutually differentially connected axles and a steering transmission mechanism that transmits oppositely directive forces to the respective axles.
2. Related Art\
Conventionally, as disclosed in Japan Patent Laid Open Gazette Nos. Sho 62-28,554 and Hei 1-234,644, and U.S. Pat. Nos. 6,141,947 and 4,771,856, and others, there is a well-known belt type stepless transmission having a double pulley, namely, a variator. Additionally, there is a well-known vehicle such as a mower tractor having the belt type stepless transmission, wherein first and second belts are looped over respective pulley portions of the double pulley so that the tension of the first belt is changed so as to change the rate of driving speed of the subsequent second belt to that of the first belt.
Especially, Japan Patent Laid Open Gazette No. Hei 1-234,644 discloses a vehicle which utilizes a speed difference between the first and second belts looped over the variator so as to change its traveling direction and speed.
The above-mentioned belt type stepless transmission using the variator is advantageouss to working vehicles such as a mower tractor requiring stepless variation of traveling speed because it is more economical than a hydrostatic stepless transmission (an HST).
Also, conventionally, there is a well-known vehicle having a steering transmission which transmits power of a prime mover in two ways so as to make a difference of rotational speed between left and right drive wheels, that is, accelerate one drive wheel and decelerate the other according to the operation of a steering device such as a steering wheel. An HST may serve as the steering transmission.
However, none of the above-mentioned documents discloses such a steering transmission. More specifically, there is no conventional vehicle having a belt type stepless transmission as mentioned above which transmits its output to such a steering transmission. Such a driving combination of the belt type stepless transmission and the steering transmission, if it is invented, will be advantageous to provide an economical working vehicle.
Furthermore, conventionally, there is a well-known small working vehicle like a mower tractor which has at least one caster for enabling a very small turn radius. However, a conventional caster provided on such a working vehicle is not steered by a steering device like a steering wheel.
A caster which is not steerable has a disadvantage in its weakness against a side force. More specifically, if a vehicle, e.g., a mower tractor with such a caster descending a slope slantwise, the caster is oriented more downward than the driving direction of the vehicle because the weight of the vehicle is applied as a side force onto the caster. Therefore, the vehicle can descend slantwise comparatively smoothly. Then, if the vehicle is going to ascend the slope slantwise, the downwardly oriented caster is hard to turn upward because of the side force. Therefore, the vehicle cannot ascend slantwise smoothly.
Thus, it is required that a steering operational force of the steering device be forcibly applied onto the caster so as to steer the caster without disturbing the steering operation while the wheels of the casters are allowed to rotate freely according to the force applied from the ground regardless of the steering condition.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an axle driving apparatus for an economical vehicle which turn has a small turn radius and whose traveling speed varies steplessly.
To achieve the object, an axle driving apparatus according to the present invention is suitable to a vehicle having a prime mover and a belt type stepless transmission. The axle driving apparatus comprises a pair of axles connected to respective drive wheels, a propelling transmission mechanism and a steering transmission mechanism. The propelling transmission mechanism is drivingly connected to said prime mover through said belt type stepless transmission so as to transmit speed-variable output rotation of said belt type stepless transmission to both said axles, thereby rotating said axles together at various speeds in a common direction selected from two opposite directions for forward and backward traveling of said vehicle. The steering transmission mechanism is drivingly connected to said prime mover so as to transmit two oppositely directive output rotations to said respective axles, thereby differentially rotating said axles at various differences of rotational speed between said axles.
An accelerator such as a pedal is operatively connected to said belt type transmission so as to change the output rotational speed of said propelling transmission mechanism. A steering operation device such as a steering wheel is operatively connected to said steering transmission so as to change the output rotational speed of said steering transmission.
The steering transmission mechanism may comprise a hydrostatic transmission.
The pair of axles may be differentially connected to each other through a first differential mechanism. In this case, said first differential mechanism transmits the output rotation of said propelling transmission mechanism to both said axles, and allows said axle to be differentially rotated by the oppositely directive output rotations of said steering transmission mechanism transmitted to said respective axles.
Furthermore, a second differential mechanism driven by said steering transmission mechanism may be provided so as to generate two oppositely rotational forces applied onto said respective axles.
A housing of the axle driving apparatus may incorporate the axles, the propelling transmission mechanism and the steering transmission mechanism together. Furthermore, the first and second differential mechanisms may be disposed together in the housing.
The housing may comprise a first chamber in which the axles, the propelling transmission mechanism and the first and second differential mechanisms are disposed, and a second chamber in which the steering transmission mechanism is disposed.
Alternatively, the axle driving apparatus may comprise at least first and second housings. The first housing may incorporate the axles and the propelling transmission mechanism, and further, the first differential mechanism. The second housing may incorporate the steering transmission mechanism, and further, the second transmission mechanism. In this case, a transmission mechanism may be interposed between the first and second housings so as to transmit the two oppositely directive output rotations of the second differential mechanism to the respective axles.
The belt type stepless transmission may be constructed as follows.
A pair of first and second belts are looped over a variator pulley such as a double pulley. The first belt receives the power of the prime mover prior to the second belt. The first belt may be driven at a constant speed determined according to the output rotational speed of the prime mover. The first belt is looped over a first idler pulley for tension variation th
Abend Robert
Ishii Norihiro
Okada Hideaki
Winfree Krista
Lum L.
Morris Lesley D.
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